1. Field Of The Invention
The present invention generally relates to a refrigerant compressor, and more particularly, to a wobble plate type refrigerant compressor used in an automotive air conditioning system.
2. Description Of The Prior Art
A wobble plate type compressor suitable for use as in an automobile cooling system is described in U.S. Pat. No. 4,444,549 to Takahashi. In such a compressor, rotation of the drive shaft is converted into reciprocating motion of a plurality of pistons through a cam rotor having a sloping end surface fixedly mounted on an inner end of the drive shaft and a wobble plate disposed on the sloping end surface through a needle bearing. The wobble plate is supported on a fixed member such as a cylinder block so that the wobble plate is prevented from rotating but is nutatable or able to wobble. Thus, the wobble plate wobbles by rotation of the cam rotor, and the plurality of piston rods connected to the wobble plate are reciprocated to compress fluid within a like plurality of cylinders.
In a known supporting mechanism for the wobble plate of the above described compressor, a first bevel gear is fixed to the wobble plate at the central portion thereof. A second bevel gear, which engages the first bevel gear, is supported on the cylinder block in such a manner that the rotation of the second bevel gear is prevented. The second bevel gear is formed on the end of a cylindrical rod, which supports the wobble plate and enables it to nutate. The cylindrical rod is supported in the center bore formed in the cylinder block. Both bevel gears are provided with ball seats. Thus, the wobble plate is prevented from rotating by the engagement between both bevel gears, and is able to nutate along the ball surface.
A supporting mechanism for a wobble plate in a wobble plate compressor is described in U.S. Pat. No. 4,221,545 to Terauchi. This supporting mechanism includes a cylindrical support portion mounted in a center bore formed in the cylinder block. The cylindrical support portion supports one of the bevel gears supporting the wobble plate. In such a supporting mechanism, a pair of grooves is axially formed on the outer surface of the cylindrical portion and on the inner surface of the central bore. These grooves oppose each other and form a chamber in a square pillar configuration. A metal key is fittingly inserted in the chamber. When the compressor operates and the wobble plate nutates, the key-groove mechanism prevents the rotational motion of the cylindrical portion.
In the above construction, during operation of the compressor, the cylindrical support portion continuously undergoes torque which tends to rotate the cylindrical support portion in the rotational direction of the drive shaft due to the gas pressure reaction force received by the wobble plate through the pistons and piston rods. The magnitude of this torque periodically fluctuates because the pistons reciprocate out of phase in their respective cylinders. The periodical torque fluctuation on the cylindrical support portion causes an undesirable vibration of the compressor housing. This undesirable vibration is propagated to an automobile passenger compartment as an offensive noise.